Fiberglass boats are typically constructed using an inner and outer fiberglass skin separated by a balsa wood core. The balsa wood core is in the form of small separate blocks preattached to a fabric or fabric like material mesh on one side only. This allows the separate blocks to tilt in two directions relative to each other to readily follow the convex contours of a boat. The spaces between the separate blocks are called veins.
While the balsa wood is very light weight and offers adequate crush resistance (on end grain), it is quite vulnerable to water infiltration between the fiberglass skins of a boat which in time may cause the core to decay and then eventually to rot. Typically when this happens, the boat owner puts off repair until the damage is extensive or structural integrity is compromised since the current method of repair is drastic. This expensive procedure involves de-skinning of entire outer fiberglass covering, replacement of the damaged balsa core, and then replacement of the outer skin. This entails hundreds of person-hours of effort and can take a boat out of service for an entire season.
Examination of the prior art reveals several patents related to localized repair of non-metallic structures or objects. U.S. Pat. No. 2,307,958 of Hellier relates to a method of repairing rubber vehicle tires by using air pressure to locate and dry ply separations, by injecting the dry air through a hole with a hollow needle. A cement is then injected to reattach the separated plies.
U.S. Pat. No. 4,236,951 of Krchma et al. relates to a method of treating blisters in asphaltic membrane covered roofs. A selected liquid hydrocarbon miscible with the asphalt of the membrane is introduced through a flexible hose with a puncture output nozzle, and the liquid hydrocarbon is used to heal the localized blistering of the asphalt.
U.S. Pat. No. 4,260,439 of Speer is related to an apparatus and method of plastic repair such as of vinyl seat covers. It involves the use of a tool with a narrow jet of heated air to cure a heat curable repair compound.
Clearly these patents do not teach techniques which can be applied to the repair of fiberglass boat hulls. However, U.S. Pat. No. 5,622,661 of Cederstrom is a method of localized repair of surface blisters of laminated plastic objects including fiberglass boat hulls. Cederstrom '661 is primarily involved with osmosis type damage to the exterior boat hull skin. Using a combination of controlled heat or cooling with mechanical action of a strong compressed air jet, in Cederstrom '661 the damaged area is cleaned and dried in a single operation using a HYAB-osmosis tool. Damaged material below the skin is not removed; instead it is reinforced with a penetrating epoxy.
A similar system is noted in the website of Star Distributing Corporation of Mystic CT in their excerpt entitled “Cost Effective Restoration of Decay in Wooden Core Fiberglass Boats©”. Star Distributing describes a time-consuming method for repairing wood damaged boat hulls by tapping the boat with a mallet to estimate wood damaged areas by listening for hollow echo sounds, drilling holes in those estimated areas, letting the wood damaged areas dry by ambient air and heat, and then pouring Clear Penetrating Epoxy Sealer (CPES) into the estimated damaged portions of a hull. The method of Star Distributing does not physically remove damaged core; it just treats it with poured CPES. The method of Star Distributing dries out areas with rudimentary ventilation and heat, but not with a system of vacuum plates and sources to facilitate controlled drying and removal of moisture. The only mention of vacuuming in Star Distributing is to a usual domestic vacuum cleaner, but Star Distributing uses a vacuum to remove drill waste, airborne fiberglass particles and water leaking from the lowest drilled hole.
In addition, the method of Star Distributing does not physically remove damaged wood core areas; it only treats drill-exposed areas with poured-in CMES, leaving unexposed, damaged wood core areas which may not be in contact with the CPES, and which may cause further wood rot damage in the future.
Initially, tapping the surface is used by both Star Distributing and optionally by the present invention. But the present invention goes much further. After initial tapping, then the present invention uses the moisture meter/infrared camera, which can accurately predict not just hollow areas, but non-hollow, moisture-ridden areas. The present invention uses an analytical grid pattern, dries wood-infested areas with heat and vacuum, then re-tests the dried areas with the moisture meter/infrared camera, after using the vacuum plate sub-system.
Star Distributing does not remove damaged areas; it only treats them with CMES. In contrast, the present invention uses augers and bits to remove out rotted core; Star Distributing only dries it.
The present invention uses moisture meters to locate water. The present invention uses grids to make moisture location more accurately, and to take notes for future moisture testing. But Star Distributing just pokes holes to examine wood thereat.
If there is water present, Star Distributing uses a vacuum cleaner to remove water at lowest point. The present invention uses vacuum to pull in air from upper holes and leaves it on for days, to facilitate drying. The present invention's continuous vacuuming facilitates fast drying of the core. Star Distributing dries by allowing approximately 1 week drying. But the present invention uses multiple measuring and monitoring with moisture meters and similar devices to ascertain proper drying.
Both Star Distributing's and the present invention's techniques are minimally invasive. But the present invention removes rotted sections of wood core and dries out non-rotted wet areas. Unlike Star Distributing, the present invention uses flexible cable tools and bits to remove rotted wood. The present invention preferably uses chopped fiberglass and epoxy to replace wood core. Star Distributing physically fills bare areas where the present invention removes rotted wood. But Star Distributing, after drying the wood core (whether bad or good) doesn't teach removing wood rot. Additionally, Star Distributing relies heavily by using the mallet tapping to locate holes representing separation of wood from fiberglass (de-lamination). Such a reliance does not rise to the level of sophistication of the present invention, which can detect moisture infested areas even if there is no separation of the fiberglass skin from the adjacent water infested wood core areas.
After drying by ambient air over time (one week), Star Distributing uses liquid CPES that is soaked up by wood that takes a long time to dry. After ambient drying, Star Distributing adds another CPES in-filling. The CPES coat is poured in to replace wood lignum lost to bacterial consumption. In contrast, the present invention is removing and replacing the damaged wood.
Unlike Star Distributing, the present invention also has optional preventive maintenance. Star Distributing does not remove damaged wood, but fills drilled plug holes with Fill It and Layup and Laminating Epoxy (LLE). Star Distributing's main emphasis is use of poring in CPES to the damaged wood.
Clearly, the repair methods of Cederstrom '661 and Star Distributing are different from the present invention. Cederstrom '661 and Star Distributing do not extend the method to a systematic analysis of a fiberglass boat hull having a balsa wood core, by using moisture meter techniques to locate damaged areas not visible to the tapping or to the naked eye, and to heat and remove the damaged wood core with accurately measured minimal incisions of the fiberglass boat outer skin.
The invention of U.S. Pat. No. 5,277,143 of Franguela, Ship Hull Repair Apparatus, describes a device that can be rapidly deployed to repair a breach in the hull of a boat. It acts to plug the hole in the hull and is designed to be installed by a diver from the exterior in an emergency to stem the flow of water into the boat if the breach is below the water line. This apparatus will seal a hole in the hull of any type of construction (eg.—metal, fiberglass, wood) as long as it is sized to be compatible with the damage.
FIG. 1 of Franguela '143 shows the method of installation by a diver. FIG. 1A of Franguela '143 shows a perspective view of the apparatus showing the mounting plate (sealing disk) 15 with two pneumatic storage cylinders 39 and 40 which contain compressed air or other gas to operate the apparatus. The crossectional side view of FIG. 4 permits one to quickly grasp the operational features of the apparatus. In this view, the configuration is as stored and prior to installation. It will be appreciated that four legs (see FIG. 2) 20 through 23 would be pushed through the hull breach protruding into the inside of the boat hull. Pneumatic piston 34 within cylinder 16 is poised to pull on cables 37 which will pivot legs 20 through 23 into the configuration shown in FIG. 7 upon pressure released from pneumatic storage cylinder 44. This action locks the apparatus to the side of the hull aided by distal hooks such as 27 and 28.
At this time, compressed gas is released from cylinder 39 to inflate annular sealing bladder 38 to form a water tight seal against the boat hull.
Although the repair is complete, there will be some hydrodynamic drag from the apparatus extending somewhat from the hull surface if below the water line. If above the water line or close to it, the repair also imposed aesthetic problems. Also, the repair may lose viability after long term use due to possible permeation of compressed gas through the flexible sealing bladder. For these reasons, the invention of Franguela '143 is considered to be an emergency and temporary repair apparatus.
In contrast to Franguela '143, the present invention is a repair system and method for fiberglass boats. The present invention is a system for locating core damage in fiberglass boat hulls while in dry dock, removing damaged wood core and repairing water intrusion damage to the damaged wood core areas. Further, drying apparatus involving the use of vacuum pumps and heaters are used to prepare the damaged areas for permanent repair. The method of the present invention is not designed to repair a hull breach which transverses both the outer and inner skins of a fiberglass boat, nor is the repair method applicable to wood or metal hull construction. Both the method and apparatus of the present invention bear no relation to the repair apparatus of Franguela '143.